1. Technical Field of the Invention
The present invention relates to the administration of at least one hydroxylated urea compound for combating signs of aging of the skin and mucous membranes.
2. Description of Background and/or Related and/or Prior Art
Women, and even men, currently have a tendency to wish to appear young for as long as possible and consequently wish to soften signs of aging of the skin, which are reflected in particular by wrinkles and fine lines, thinning of the epidermis, and/or skin with a flabby and withered appearance. On that subject, advertising and fashion promote products intended to retain a radiant and wrinkle-free skin for as long as possible, these being signs of a young skin, all the more so as the physical appearance affects the mind and/or the morale.
The skin is composed of two compartments, a surface compartment, the epidermis, and a deeper compartment, the dermis, which interact. The natural human epidermis is composed mainly of three types of cells, which are the keratinocytes, which form the vast majority, the melanocytes and the Langerhans cells. Each of these cell types contributes, via the specific functions thereof, to the essential role played by the skin in the body, in particular the role of protecting the body from external attacks, known as “barrier function”
The epidermis is conventionally divided into a basal layer of keratinocytes, which constitutes the germinal layer of the epidermis, a “prickle cell” layer, composed of several layers of polyhedral cells positioned on the germinal layers, one to three “granular” layers, composed of flattened cells comprising distinct cytoplasmic inclusions, keratohyalin granules, and finally the horny layer (or stratum corneum), composed of a combination of layers of keratinocytes at the terminal stage of their differentiation, known as corneocytes. Corneocytes are anucleate cells composed mainly of a fibrous material comprising cytokeratins which is surrounded by a horny envelope.
The dermis provides the epidermis with a firm support. It is also its nutrient element. It is mainly composed of fibroblasts and of an extracellular matrix composed predominantly of collagen, of elastin and of a substance referred to as ground substance. These components are synthesized by the fibroblasts. Leukocytes, mastocytes or even tissue macrophages are also found therein. Finally, blood vessels and nerve fibers pass through the dermis.
Cohesion between the epidermis and the dermis is provided by the dermal-epidermal junction.
New keratinocytes are continuously being produced in the epidermis in order to compensate for the continuous loss of epidermal cells at the horny layer.
However, during aging, epidermal proliferation and differentiation may be physiologically disrupted and a tendency for these two mechanisms to come into imbalance may be observed.
In addition, a deterioration in the proteasome system with age has been demonstrated (Friguet et al., 2002, Scientific World Journal). This may in part be related to an accumulation of oxidized proteins and thus to cell dysfunctioning (Dunlop, Rodgers et al., 2002; Szweda, Friguet et al., 2002). It will therefore be desirable to stimulate the activities in order to make up this deterioration.
The suggestion has been made that the stock of free amino acids in the stratum corneum decreases with the state of cutaneous dryness (Tanaka, Okada et al., 1998), which is accentuated in aged skin. These amino acids originate from the proteolysis of filaggrin. It is thus possible naturally to compensate for this deterioration in proteolysis of filaggrin by stimulating the protease activities for degradation of this protein.
Finally, the maturing of the HE (horny envelope), which can be detrimentally affected with age, is under the control of transglutaminase activities, themselves activated by proteolysis of a precursor; the activation of proteases involved in this processing would thus be of use.
Therefore, need continues to exist for novel means for combating one or more of these phenomena in order to prevent; delay or reduce the signs related to aging of the skin or mucous membranes.